I have a problem that is not addressed by the numerous articles on MVVM grouping that I have read.
I am writing a WPF application. Here are some excepts from classes that are relevant to my question - first the MainViewModel:
public class MainViewModel
{
public ObservableCollection<Recipe_OverViewModel> RecipeOverViews {get ; set;}
....[omitted extraneous lines]....
The class that is used as the observable collection of Recipes in the MainViewModel:
public class Recipe_OverViewModel
{
public Recipe TargetRecipe { get; set; }
public override string ToString()
{
return TargetRecipe.Parent_Name;
}
....[omitted extraneous lines]....
and The Class that is taken from the database, that is the actual Recipe
public partial class Recipe
{
[Required]
[StringLength(1000)]
public string Parent_Name { get; set; }
[Required]
[StringLength(60)]
public string Recipe_Name { get; set; }
public override string ToString()
{
return Parent_Name;
}
public int CompareTo(object obj)
{
return Parent_Name.CompareTo(((Recipe)obj).Parent_Name);
}
....[omitted extraneous lines]....
Each class has more properties and methods and so on, but these are enough to explain what I am asking.
The Recipe_OverViewModel is the view model for a control (Recipe_OverView) that displays the properties of the recipe. In the MainViewModel, I have the following xaml (extracted from the larger file):
<Window x:Class="RecipeApp.UI.MainWindow"
....[omitted extraneous lines]....
xmlns:vm="clr-namespace:RecipeApp.UI.ViewModel"
>
<Window.Resources>
<DataTemplate DataType="{x:Type vm:Recipe_OverViewModel}" x:Key="Recipe_DT" x:Name="Recipe_DT">
<control:Recipe_OverView Width="{Binding ActualWidth,ElementName=ListWidth}"/>
</DataTemplate>
<CollectionViewSource x:Key="SortedRecipeOverViews" Source="{Binding RecipeOverViews}">
<CollectionViewSource.SortDescriptions>
<scm:SortDescription PropertyName="TargetRecipe"/>
</CollectionViewSource.SortDescriptions>
<CollectionViewSource.GroupDescriptions>
<PropertyGroupDescription PropertyName="TargetRecipe"/>
</CollectionViewSource.GroupDescriptions>
</CollectionViewSource>
</Window.Resources>
....[omitted extraneous lines]....
<ListView ItemsSource="{Binding Source={StaticResource SortedRecipeOverViews}}"
ItemTemplate="{StaticResource Recipe_DT}">
</ListView>
This list view correctly displays the list of recipes in the listview, with each row containing the Recipe_OverView control. However, I cannot get the grouping to work correctly. I would like to group the listview by the Parent_Name property of the Recipe associated with each Recipe_OverViewModel. My attempt looked like this, following the Microsoft HowTo:
<ListView Grid.Row="1" Grid.Column="1"
ItemsSource="{Binding Source={StaticResource SortedRecipeOverViews}}"
ItemTemplate="{StaticResource Recipe_DT}"
>
<ListView.GroupStyle>
<GroupStyle>
<GroupStyle.ContainerStyle>
<Style TargetType="{x:Type GroupItem}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type GroupItem}">
<Expander IsExpanded="true">
<Expander.Header>
<TextBlock Text="{Binding Path=ParentName}" />
</Expander.Header>
</Expander>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</GroupStyle.ContainerStyle>
</GroupStyle>
</ListView.GroupStyle>
</ListView>
However, all I get from that is as many empty (no ParentName populated) headers as there are recipes in the collection and a Binding Failure that tells me the "ParentName property not found on object of type CollectionViewGroupInternal." I get the expander buttons, but there is nothing within the expanded groups:
I thought I understand that that means that the binding is looking in the Recipe_OverViewModel for the ParentName property, but even when I added this as a property in the Recipe_OverViewModel and populated it, I still got this error, so now I am confused and have the following questions:
Where is the binding on the ListView actually looking?
How should I direct it to look at the Recipe_OverViewModel.TargetRecipe.ParentName (or is it impossible)?
I would really appreciate help on this matter, so many articles take so much simpler examples, and I cannot work out how to extend it to my case!
Where is the binding on the ListView actually looking?
It looks for a property of the CollectionViewGroupInternal class.
This class has a Name property that returns the value of the property that you group by, i.e. TargetRecipe, and an Items property that returns the collection of objects that belongs to the current group.
So, if I understand your setup correctly, you could try to bind to the Parent_Name property of the first item in the group:
<Expander.Header>
<TextBlock Text="{Binding Items[0].Parent_Name}" />
</Expander.Header>
The ItemsSource is bound to the SortedRecipeOverViews, which in turn is bound to the RecipeOverViews collection.
The item type of this collection is Recipe_OverViewModel.
And this type doesn't have a ParentName property.
There is a Parent_Name property, BUT not in the Recipe_OverViewModel type, but in the Recipe type.
And the Recipe_OverViewModel type has a property of this type.
In general, you have some kind of mess of types, their names and their properties, binding paths.
Perhaps you copied something wrong into the topic?
Based on my own guess, try applying a binding like this:
<Expander.Header>
<TextBlock Text="{Binding Path=TargetRecipe.Parent_Name}" />
</Expander.Header>
Related
I'm currently working on a WPF .NET 4.7 application and I use Infragistics WPF controls version 18.
I need to create a custom XamComboEditor which has a XamDataTree inside. Thus a ComboBox with a Tree selection inside.
The Tree selection works fine without the XamComboEditor and looks like this:
<iWPF:XamDataTree ItemsSource="{Binding Locations}">
<iWPF:XamDataTree.GlobalNodeLayouts>
<iWPF:NodeLayout Key="Locations" TargetTypeName="LocationViewModel" DisplayMemberPath="Name"/>
<iWPF:NodeLayout Key="ChildLocations" TargetTypeName="string"/>
</iWPF:XamDataTree.GlobalNodeLayouts>
</iWPF:XamDataTree>
My XamDataTree is bound to an observable collection Locations:
public ObservableCollection<LocationViewModel> Locations { get; set; } = new ObservableCollection<LocationViewModel>();
public class LocationViewModel
{
public int Id { get; set; }
public string Name { get; set; }
public List<LocationViewModel> ChildLocations { get; set; } = new List<LocationViewModel>();
}
I need to use the style setter on my XamComboEditor to put the XamDataTree inside the combobox.
My problem is now, I don't know how to achieve this, or how to pass the context from the XamComboEditor further to the XamDataTree.
I tried the following, in vain:
<iWPF:XamComboEditor ItemsSource="{Binding Locations}">
<iWPF:XamComboEditor.ComboBoxStyle>
<Style TargetType="ComboBox">
<Setter Property="ItemTemplate">
<Setter.Value>
<DataTemplate>
<iXaml:XamDataTree ItemsSource="{Binding .}">
<iXaml:XamDataTree.GlobalNodeLayouts>
<iXaml:NodeLayout Key="Locations" TargetTypeName="LocationViewModel" DisplayMemberPath="{Binding Name}"/>
<iXaml:NodeLayout Key="ChildLocations" TargetTypeName="string"/>
</iXaml:XamDataTree.GlobalNodeLayouts>
</iXaml:XamDataTree>
</DataTemplate>
</Setter.Value>
</Setter>
</Style>
</iWPF:XamComboEditor.ComboBoxStyle>
</iWPF:XamComboEditor>
Do you know how to solve this issue? Do you know how to pass the data context from the parent control to, let's say, the child control? Or rather, how to put the XamDataTree inside the XamComboEditor?
If I understood this correctly, the DataContext of your XamlDataTree is no what you expect it to be (the Locations bound in you XamComboEditor).
One way to solve this problem is to specify the source of the path in your Binding markup extension.
You can use the {x:Reference ...} markup extension to reference a named controled in your control tree.
<iWPF:XamComboEditor x:Name="comboEditor" ItemsSource="{Binding Locations}">
<iWPF:XamComboEditor.ComboBoxStyle>
<Style TargetType="ComboBox">
<Setter Property="ItemTemplate">
<Setter.Value>
<DataTemplate>
<iXaml:XamDataTree ItemsSource="{Binding Source={x:Reference Name=comboEditor}, Path=DataContext.Locations}">
<iXaml:XamDataTree.GlobalNodeLayouts>
<iXaml:NodeLayout Key="Locations" TargetTypeName="LocationViewModel" DisplayMemberPath="{Binding Name}"/>
<iXaml:NodeLayout Key="ChildLocations" TargetTypeName="string"/>
</iXaml:XamDataTree.GlobalNodeLayouts>
</iXaml:XamDataTree>
</DataTemplate>
</Setter.Value>
</Setter>
</Style>
</iWPF:XamComboEditor.ComboBoxStyle>
</iWPF:XamComboEditor>
You can also achieve this without naming your controls with the RelativeSource property in the Binding (something like RelativeSource={RelativeSource AncestorType=iWPF:XamComboEditor}).
The WPF version of this question is here: But it hasn't been answered and I don't know if the UWP TreeView will have the same answer.
I'm trying to add a DataTemplateSelector to the new UWP TreeViews that were just added to windows 10 version 1803 but it isn't working. It is documented here how to use the XAML TreeView Control and even shows how to modify the template to change the Item Datatemplate which works fine. I need to use a datatemplate selector since each of my nodes is using different objects and I need them displayed differently. The TreeView.Node.Content is being set just fine and everything works except it is passing null over to the datatemplateselector in the Object parameter.
Here is my code: (same as the example from Microsoft just with using ItemTemplateSelector)
<Style TargetType="TreeView">
<Setter Property="IsTabStop" Value="False" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="TreeView">
<TreeViewList x:Name="ListControl"
ItemTemplateSelector="{StaticResource CardSelector}"
ItemContainerStyle="{StaticResource TreeViewItemStyle}"
CanDragItems="True"
AllowDrop="True"
CanReorderItems="True">
<TreeViewList.ItemContainerTransitions>
<TransitionCollection>
<ContentThemeTransition />
<ReorderThemeTransition />
<EntranceThemeTransition IsStaggeringEnabled="False" />
</TransitionCollection>
</TreeViewList.ItemContainerTransitions>
</TreeViewList>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
Does anyone have any insight or experience on this? My datatemplateselector "CardSelector" works fine and I have been using it in several places without any trouble.
So the point of my question isn't to get anything that I have working but to see if the TreeViewControl works with a DataTemplateSelector. I only have "CardTemplateSelector" in there because I use it in several other places of my app and I know it works. My question is really a "yes, treeview works with a selector" or "no it doesn't" I'm really looking for someone else to try it with their own test template selector and to let me know if they can get it working. Any specific code from me is not relevant to the question. Just see if you can get it to work with whatever selector you want
Yes. The TreeView work well with ItemTemplateSelector.
I used the all code in the document and create a custom class like the following:
public class Test
{
public string Name { get; set; }
}
I made another DataTemplate like this:
<DataTemplate x:Key="TreeViewObjDataTemplate">
<Grid Height="44">
<TextBlock
Text="{Binding Content.Name}"
HorizontalAlignment="Left"
VerticalAlignment="Center"
Style="{ThemeResource BodyTextBlockStyle}"/>
</Grid>
</DataTemplate>
My CardTemplateSelector class is the following:
public class CardTemplateSelector: DataTemplateSelector
{
public DataTemplate TreeViewItemDataTemplate { get; set; }
public DataTemplate TreeViewObjDataTemplate { get; set; }
protected override DataTemplate SelectTemplateCore(object item)
{
TreeViewNode treeViewNode = item as TreeViewNode;
if (treeViewNode.Content is StorageFolder|| treeViewNode.Content is StorageFile)
{
return TreeViewItemDataTemplate;
}
if (treeViewNode.Content is Test)
{
return TreeViewObjDataTemplate;
}
return base.SelectTemplateCore(item);
}
protected override DataTemplate SelectTemplateCore(object item, DependencyObject container)
{
return SelectTemplateCore(item);
}
}
I just add the new lines code in MainPage.xaml.cs:
TreeViewNode objnode = new TreeViewNode();
Test test = new Test() {Name="Parent"};
objnode.Content = test;
objnode.IsExpanded = true;
objnode.HasUnrealizedChildren = true;
sampleTreeView.RootNodes.Add(objnode);
The following is the whole xaml page resource code:
<Page.Resources>
<DataTemplate x:Key="TreeViewItemDataTemplate">
<Grid Height="44">
<TextBlock
Text="{Binding Content.DisplayName}"
HorizontalAlignment="Left"
VerticalAlignment="Center"
Style="{ThemeResource BodyTextBlockStyle}"/>
</Grid>
</DataTemplate>
<DataTemplate x:Key="TreeViewObjDataTemplate">
<Grid Height="44">
<TextBlock
Text="{Binding Content.Name}"
HorizontalAlignment="Left"
VerticalAlignment="Center"
Style="{ThemeResource BodyTextBlockStyle}"/>
</Grid>
</DataTemplate>
<local:CardTemplateSelector x:Name="CardTemplateSelector" TreeViewItemDataTemplate="{StaticResource TreeViewItemDataTemplate}" TreeViewObjDataTemplate="{StaticResource TreeViewObjDataTemplate}"></local:CardTemplateSelector>
<Style TargetType="TreeView">
<Setter Property="IsTabStop" Value="False" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="TreeView">
<TreeViewList x:Name="ListControl"
ItemTemplateSelector="{StaticResource CardTemplateSelector}"
ItemContainerStyle="{StaticResource TreeViewItemStyle}"
CanDragItems="True"
AllowDrop="True"
CanReorderItems="True">
<TreeViewList.ItemContainerTransitions>
<TransitionCollection>
<ContentThemeTransition />
<ReorderThemeTransition />
<EntranceThemeTransition IsStaggeringEnabled="False" />
</TransitionCollection>
</TreeViewList.ItemContainerTransitions>
</TreeViewList>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</Page.Resources>
So far I have answered your question. But I still want to let you know How to ask a good question. In my above comments, I asked you to provide the relevant code, then I could quickly reproduce your question and help you diagnose it. But you said I'm really looking for someone else to try it with their own test template selector and to let me know if they can get it working.. It's Ok. You could see that only I replied. You asked this question for many days. No other community members helped you on this question. That's why I ask you to post some code here. If you provide the relevant code here, I believe many community members will be glad to help you on this question. I really hope you could understand it.
There seems to be confusion about where to apply the DataTemplate. And the all important TargetType is ignored.
If you want a handle on the data item in your custom DataTemplateSelector, you need to:
OPTION 1
Apply the DataTemplateSelector on TreeView.ItemTemplateSelector
Make sure that the DataTemplates have TreeViewNode as the target type.
Only then the data item of the TreeViewNode is supplied to the SetTemplateCore(object item) and SetTemplateCore(object item, DependencyObject container) overrides of your custom DataTemplateSelector.
A working example is found here: Pictures and Music library tree view
OPTION 2
Apply the DataTemplateSelector on TreeViewItem.ContentTemplateSelector
Make sure that the DataTemplates have [YOUR-DATA-TYPE] as the target type
In the TreeView.ItemTemplate bind the DataContext AND Content property to [YOUR-DATA-TYPE], i.e.
<TreeView.ItemTemplate>
<DataTemplate x:DataType="[YOUR-DATA-TYPE]">
<TreeViewItem DataContext="{Binding}" ... Content="{Binding}">
<TreeViewItem.ContentTemplateSelector>
<YourDataTemplateSelector.TemplateA>
<DataTemplate x:DataType="[YOUR-DATA-TYPE]">
...
// YourDataTemplateSelector
protected override DataTemplate SelectTemplateCore(object item, DependencyObject container)
{
if (item == null) return null;
return (([YOUR-DATA-TYPE])item).IsSomething ? TemplateA : TemplateB;
}
I've been following this guide (among other resources) and have the ListBox grouping my list of Users successfully. The problem now is two-fold;
The header of each group is not displaying what it is grouping by (at present, just an int).
I would like, if possible, for the header to be a lookup. (I'm using Entity Framework, so this could be made redundant by using an Include(u => u.Ref_Department) on the query to get the list of Users.)
The data is as follows;
Users
idUser
id_Department
Name
Department
idDepartment
DepartmentName
The XAML;
<Grid>
<Grid.Resources>
<CollectionViewSource x:Key="lsUsers" Source="{Binding RelativeSource={RelativeSource AncestorType={x:Type Window}}, Path=_Users}">
<CollectionViewSource.GroupDescriptions>
<PropertyGroupDescription PropertyName="id_Department"/>
</CollectionViewSource.GroupDescriptions>
</CollectionViewSource>
</Grid.Resources>
<ListBox ItemsSource="{Binding Source={StaticResource lsUsers}}">
<ListBox.GroupStyle>
<GroupStyle>
<GroupStyle.ContainerStyle>
<Style TargetType="{x:Type GroupItem}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate>
<Expander Header="{Binding id_Department}" IsExpanded="True">
<ItemsPresenter/>
</Expander>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</GroupStyle.ContainerStyle>
</GroupStyle>
</ListBox.GroupStyle>
</ListBox>
</Grid>
_Users is a List<Users> property of the class, which is obviously working fine anyway, it's just the header that is falling down for some reason and I don't really understand why.
There is a highlight/warning on the <Expander Header... line under id_Department that says "Cannot resolve symbol 'id_Department' due to unknown DataContext"
Update
If I change the <Expander Header... binding to Name, it displays the id_Department. Not sure how/why that works and I'm not sure that it'll help with Point 1 above.
while Using GroupStyle you have only the following Binding Propoerties:
Name: which is the Name of group property that make the grouping based on
ItemCount: which is the Rows Count of each grouping record
and if you want another property based on grouping item you should use Converter but when using:
{Binding Converter="{StaticResource yourConverter}"
consider that the value of Converter is CollectionViewGroup which is the list of objects or rows that is in the grouped base item.
As #safi implies, because the GroupItem is what is being styled you only have the Name and ItemCount properties to bind to.
It sounds like you are trying to group by department but want to see the department name instead of the ID. Therefore you should add a string Department property to your Users class and group on that instead of the department ID property.
You can control the ordering of the groups by changing the SortDescriptions of the collection view. For example, if you want to group by department name but still see departments listed in ID order rather than alphabetically then group by the name and also sort by the ID, like this:
ICollectionView view = CollectionViewSource.GetDefaultView(_Users);
view.GroupDescriptions.Add(new PropertyGroupDescription("DepartmentName"));
view.SortDescriptions.Add(new SortDescription("DepartmentId", ListSortDirection.Ascending));
view.SortDescriptions.Add(new SortDescription("UserName", ListSortDirection.Ascending));
I've used different property names here but you get the idea.
I'm writing a WPF application. I want it to display data in ListBox from different sources. I want to make some common source interface like
interface IDataSource<T>
{
ObservableCollection<T> Elements { get; set; }
DataTemplate ElementDataTemplate { get; set; }
}
But I don't know which is the best type or types which I should user for IDataSource. I can make it UserControl, but it seems to be unnecessary, because my DataSource is not user control. The main problem is with ElementDataTemplate. How can I properly manage it not from UserControl class? Should I care another helper UserCntrol class and call something like (new MyUserControl).FindResource("ElementsDataTemplate") to obtain datatemplate or there is more fine way to keep and get DataTemplate?
You can simply apply a data template for a specific type in the resource section of the corresponding view:
<!-- Items may be of type ViewModel1 and ViewModel2 -->
<ItemsControl ItemsSource="{Binding Items}">
<ItemsControl.Resources>
<DataTemplate DataType="{x:Type vm:ViewModel1}">
<TextBlock Text="{Binding PropertyA}" />
</DataTemplate>
<DataTemplate DataType="{x:Type vm:ViewModel2}">
<TextBlock Text="{Binding PropertyB}" />
</DataTemplate>
</ItemsControl.Resources>
</ItemsControl>
So there is no need for the interface.
I have a ListBox that its ItemsSource is given from a class based on the data binded items template. I want to find ListBox.SelectedItem position relative to the ListBox. Since I've used a class to feed ItemsSource, I'm not be able to cast ListBox.SelectedItem (which has a type of object) to the ListBoxItem. (Instead I should cast it to the source class type.)
What's the way? -Thanks
Details: (Arbitrary)
There is a ListBox which implements a Style like so:
<Style x:Key="MyListBoxStyle" TargetType="{x:Type ListBox}">
<Setter Property="ItemTemplate">
<Setter.Value>
<DataTemplate>
<Border ...>
<StackPanel ...>
<Image Source="{Binding Path=ItemImageSource}" .../>
<TextBlock Text="{Binding Path=ItemTitle}" .../>
</StackPanel>
</Border>
</DataTemplate>
</Setter.Value>
</Setter>
</Style>
The ListBox has been used as follows:
<ListBox x:Name="MyListBox"
ItemsSource="{Binding}"
Style="{StaticResource ResourceKey=MyListBoxStyle}"/>
Also there is a class that supports MyListBox data-binding info:
internal class MyListBoxItemBinding
{
public string ItemTitle { get; set; }
public ImageSource ItemImageSource { get; set; }
}
And to feed the MyListBox:
MyListBox.ItemsSource = new List<MyListBoxItemBinding> { /* some items */ };
Now, how can I find MyListBox.SelectedItem location relative to the MyListBox?
Use ItemsControl.ItemContainerGenerator to get a reference to the item container generator for your ListBox (this is the object that creates wrappers for all your databound objects).
Then, use the ItemContainerGenerator.ContainerFromItem method to get a reference to the UIElement that represents the selected ListBoxItem.
Finally, see the answer to this question to for a way of getting the coordinates of the selected item relative to the ListBox.